As cars change over the years, so do the skillsets of mechanics who work on them (just try finding someone who can rebuild a carb or an old generator). Perhaps one of the most fascinating skills that’s on its way out is a bearing-pouring process called “babbitting,” as Road & Track describes in this excellent article.
Nowadays, people swap out engine bearings by simply replacing two bearing shell halves with new ones they can buy from the store. I did that with my 1948 Willys CJ-2A, and it was a breeze.
But many engines older than my venerable Go-Devil didn’t use these bearing inserts, but instead “babbitt bearings,” which had to be made from scratch by pouring molten babbitt (made primarily of tin, antimony and copper) between a part’s bearing surface and a mandrel. The gap between the part (which has to have its old babbitt melted and scraped out) and the mandrel made up the mould into which babbitt was poured.
Here’s a video showing part of the process:
Once the babbitt hardens, the machinest has to precisely remove the excess babbitt (to ensure the right inner diameter), drill oiling holes, and prepare the surface.
As Road & Track’s Sam Smith wrote in his piece, this whole thing is an art form:
Metallurgy is science, but the results of babbitting must be gauged by eye and feel, which means the practice includes a healthy dose of art...If your poured babbitt isn’t perfect, it will come apart under that load and take the engine with it. And there are myriad ways to make a babbitt bearing imperfect. You can pour it too quickly, too slowly, or at the wrong temperature. Or use the wrong blend of babbitt for the application, allow impurities into the melted metal . . . the list goes on.
Read the whole story and prepare to be enlightened about an outdated but captivating car-repair process conducted by only a few remaining wrenching wizards.